1. Field of the Invention
This invention relates to a hot runner probe and its equipment which can perform high-accuracy injection molding operations of synthetic resin.
2. Brief Description of the Prior Art
In general, a heater for synthetic resin injection molding consists of nichrome wires, and since this exothermic body made of nichrome wires shows only minor changes in the resistance value due to temperature changes, a step-shaped exothermic body is used to partially change temperatures, for instance, as shown in Laid-open Japanese Utility Model Application No. 56-26227.
Similarly, the heater shown in Publication Japanese Patent Application No. 4-82095 is also a cartridge-type electric heater in which nichrome wire is made into a coil-shaped resistance wire.
Now in this type of hot runner probe applied by the present applicant, a unit using a ceramic heater shown in Laid-open Japanese Patent Application No. 2-100284 is known, but the present invention relates to a composition which is composed of two kinds of ceramic heaters or a combination of one ceramic heater and another exothermic body.
In the above-mentioned heater using conventional nichrome wire, it is inconvenient to have proper temperature distribution over the entire probe, because the increase and decrease of resistance due to temperature changes are little. Also in the compositions of using two different kinds of ceramic heaters or a combination of the ceramic heater and another type of heater, it is necessary to control two different heaters respectively, and since this is impossible by operating a single control means, the composition became complicated and large in size, posing a problem of not being able to offer the invention at a reasonable price.